cxl/uapi: Tag commands from cxl_query_cmd()

It was pointed out that commands not supported by the device or excluded
by the kernel were being returned in cxl_query_cmd().[1]

While libcxl correctly handles failing commands, it is more efficient to
not issue an invalid command in the first place.  This can't be done
without additional information being returned from cxl_query_cmd().  In
addition, information about the availability of commands can be useful
for debugging.

Add flags to struct cxl_command_info which reflect if a command is
enabled and/or exclusive to the kernel.

[1] https://lore.kernel.org/all/63b4ec4e37cc1_5178e2941d@dwillia2-xfh.jf.intel.com.notmuch/

Suggested-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Ira Weiny <ira.weiny@intel.com>
Link: https://lore.kernel.org/r/20221222-cxl-misc-v4-3-62f701c1cdd1@intel.com
Signed-off-by: Dan Williams <dan.j.williams@intel.com>

diff --git a/drivers/cxl/core/mbox.c b/drivers/cxl/core/mbox.c
index 202d49dd9911845d195aeac2eb0aa5d3ed003675..fd3b13b0fb7f0ef034bd19ce5529496cd684bf8d 100644 (file)
--- a/drivers/cxl/core/mbox.c
+++ b/drivers/cxl/core/mbox.c
@@ -451,9 +451,14 @@ int cxl_query_cmd(struct cxl_memdev *cxlmd,
         * structures.
         */
        cxl_for_each_cmd(cmd) {
-               const struct cxl_command_info *info = &cmd->info;
+               struct cxl_command_info info = cmd->info;
 
-               if (copy_to_user(&q->commands[j++], info, sizeof(*info)))
+               if (test_bit(info.id, cxlmd->cxlds->enabled_cmds))
+                       info.flags |= CXL_MEM_COMMAND_FLAG_ENABLED;
+               if (test_bit(info.id, cxlmd->cxlds->exclusive_cmds))
+                       info.flags |= CXL_MEM_COMMAND_FLAG_EXCLUSIVE;
+
+               if (copy_to_user(&q->commands[j++], &info, sizeof(info)))
                        return -EFAULT;
 
                if (j == n_commands)

diff --git a/include/uapi/linux/cxl_mem.h b/include/uapi/linux/cxl_mem.h
index 459a3f7f764b7d61d2a1fc4942c3cf102432c4c7..9fe832afee3703a5a91cc0746cc069ce47b55160 100644 (file)
--- a/include/uapi/linux/cxl_mem.h
+++ b/include/uapi/linux/cxl_mem.h
@@ -72,6 +72,19 @@ static const struct {
  * struct cxl_command_info - Command information returned from a query.
  * @id: ID number for the command.
  * @flags: Flags that specify command behavior.
+ *
+ *         CXL_MEM_COMMAND_FLAG_USER_ENABLED
+ *
+ *         The given command id is supported by the driver and is supported by
+ *         a related opcode on the device.
+ *
+ *         CXL_MEM_COMMAND_FLAG_EXCLUSIVE
+ *
+ *         Requests with the given command id will terminate with EBUSY as the
+ *         kernel actively owns management of the given resource. For example,
+ *         the label-storage-area can not be written while the kernel is
+ *         actively managing that space.
+ *
  * @size_in: Expected input size, or ~0 if variable length.
  * @size_out: Expected output size, or ~0 if variable length.
  *
@@ -81,7 +94,7 @@ static const struct {
  * bytes of output.
  *
  *  - @id = 10
- *  - @flags = 0
+ *  - @flags = CXL_MEM_COMMAND_FLAG_ENABLED
  *  - @size_in = ~0
  *  - @size_out = 0
  *
@@ -91,7 +104,9 @@ struct cxl_command_info {
        __u32 id;
 
        __u32 flags;
-#define CXL_MEM_COMMAND_FLAG_MASK GENMASK(0, 0)
+#define CXL_MEM_COMMAND_FLAG_MASK              GENMASK(1, 0)
+#define CXL_MEM_COMMAND_FLAG_ENABLED           BIT(0)
+#define CXL_MEM_COMMAND_FLAG_EXCLUSIVE         BIT(1)
 
        __u32 size_in;
        __u32 size_out;